"This is the Boston Marathon -- my dream marathon. I planned on running, and qualifying and running someday," Hui-Chow said.

Hui-Chow is a busy Shock Trauma surgeon. She did not have the time to try to qualify for the race, which she has long attended as a spectator. Instead, she was chosen to run by a patient and now friend.

Last year, she was feet away from finishing the race when everything changed for her and her family.

"It means kind of like bringing the whole year, wrapping the whole year up and bring some closure to it. And I hope after I complete the marathon and get to the finish line and everyone's safe, we can sort of put this year behind us and start moving forward," Downing said.

Jackie Szimanksi, who makes her own sports drink for her runs, is also going back to Boston. She was there last year to support her brother-in-law, who was running the race. This year, she will be running with him in her first marathon.

"To hear so many people say, 'I'm going back next year. I'm going across that finish line next year.' It was very inspiring so I said, 'I want to be one of those folks.' So I want to cross that finish line," Szimanksi said.

The race is on April 21. This will be the 118th Boston Marathon, but a race like none other.